This demonstration unit facilitates the experimental investigation of the progression of the shearing force in a bar subject to point loads. Also the section principle commonly used in mechanics can be demonstrated. Due to the usage at 1/3 span of a low friction joint sensitive to shearing forces and a dynamometer, the measurements of shearing force on the bar can be recorded directly. The deflection of the bar as a result of the travel of the dynamometers and the horizontal alignment can be compensated and regulated using two adjustment bolts. The bar is loaded with graduated sets of weights that can be attached at any point on the bar. The support rollers are equipped with ball bearings.